One of processes for manufacturing a semiconductor device is a liquid process (for example, a cleaning process) which is performed by supplying a processing liquid (for example, a chemical liquid) onto a substrate such as a semiconductor wafer (hereinafter, simply referred to as “wafer”). As an apparatus configured to perform such a liquid process, there is known a single-substrate processing apparatus that holds a substrate (wafer) by a spin chuck and supplies a processing liquid onto a surface of the wafer while rotating the wafer.
The processing liquid supplied to the wafer may be dispersed from the wafer being rotated in the form of mist. In order to collect the dispersed mist, a structure called a “cup” configured to surround the wafer W is provided. One example of such a cup is described in Patent Document 1. A substrate processing apparatus described in Patent Document 1 includes a rotary cup configured to be rotated while being connected to a spin chuck; and a stationary cup provided at an outside of the rotary cup in a radial direction thereof. The mist dispersed from the wafer may be guided into the rotary cup and introduced into a flow path formed within the stationary cup. In order to avoid interference between the rotary cup that is rotated and a first cup (stationary cup) that is not rotated, a gap of an appropriate size needs to be provided therebetween.
A part of the processing liquid introduced into the flow path of the stationary cup has been already turned into the form of mist before reaching the flow path, or turns into the form of mist as a result of colliding with a wall surface of the flow path. The mist may adhere to the wafer after flowing backward through the gap between an outer surface of the rotary cup and an inner surface of the first cup. The mist adhering to the wafer may cause particle generation. In order to suppress this problem, a returning member is provided at the inner surface of the first cup. When an air current is generated in the gap between the rotary cup and the first cup in a circumferential direction of the cup at the time when the rotary cup is rotated, the returning member guides the air current downwards. Accordingly, backflow of the mist to the wafer through the gap between the rotary cup and the first cup can be greatly reduced.
With the above-described configuration, however, the flowing of the mist of the processing liquid toward the wafer through the gap cannot be suppressed perfectly. In this aspect, the description of Patent Document 1 still leaves a room for improvement.
Patent Document 1: Japanese Patent Laid-open Publication No. 2012-129462